Mechanisms of this type are used for example for clamping machine-tool carriages or for the feed of movable spindle sleeves of machine tools. In machine-tool carriages, a clamping force which acts perpendicular to the guide surface often leads to an undesired deformation of the carriage in the clamping region; in spindle sleeves, there results also an undesired deformation and a spindle deflection to the side. Most of all, in the case of spindle sleeves of modern, very precise machine tools, the clamping mechanism is supposed to hold the spindle sleeve and thus the tool spindle which is supported in said spindle sleeve securely in every axial position, without the clamping operation causing a change in the axial and radial adjustments and the adjustment of the spindle sleeve in a peripheral direction.
A clamping mechanism of this type is already known for the spindle sleeve of a machine tool in which the clamping member is arranged approximately tangentially with respect to the spindle sleeve and, with two clamping pieces which are movable relative to one another, clamps a clamping bar which is constructed on the spindle sleeve (German Patent No. 2 644 178). For reasons of a simple manufacture, the clamping pieces are cylindrical and are supported movably in a corresponding round bore in the wall of the spindle housing. Already a small lateral clearance of the clamping member in the round bore has the result that the spindle sleeve can rotate a certain amount. A further disadvantage is seen in the fact that, through wear or deformation of the clamping surfaces of the clamping bar or of the clamping pieces, forces occur perpendicular to the guide surface, that is, perpendicular with respect to the spindle axis. Since the clamping member cannot give way in this direction, the spindle sleeve is loaded in a radial direction, which is particularly disadvantageous for the exactness of the spindle. Furthermore, the possible circular-segment-shaped clamping surface of the clamping pieces is only relatively small in this construction so that, for a pregiven permissible surface pressure, only relatively small clamping forces can be produced.
A purpose of the present invention is to provide a mechanism of the above type which permits a substantially reaction-free clamping of the machine part and produces a high clamping force while having a simple method of construction.